Vortex patterns in a superconducting-ferromagnetic rod

A superconducting rod with a magnetic moment on top develops vortices obtained here through 3D calculations of the Ginzburg-Landau theory. The inhomogeneity of the applied field brings new properties to the vortex patterns that vary according to the rod thickness. We find that for thin rods (disks) the vortex patterns are similar to those obtained in presence of a homogeneous magnetic field instead because they consist of giant vortex states. For thick rods novel patterns are obtained as vortices are curve lines in space that exit through the lateral surface.Comment: 4 pages, 4 figues, Proceeding of the Sixth International Conference in School Format on Vortex Matter in Nanostructured Superconductors (VORTEX VI

Energy dependence of a vortex line length near a zigzag of pinning centers

A vortex line, shaped by a zigzag of pinning centers, is described here through a three-dimensional unit cell containing two pinning centers positioned symmetrically with respect to its center. The unit cell is a cube of side $L=12\xi$, the pinning centers are insulating spheres of radius $R$, taken within the range $0.2\xi$ to $3.0\xi$, $\xi$ being the coherence length. We calculate the free energy density of these systems in the framework of the Ginzburg-Landau theory.Comment: Submitted to Braz. Jour. Phys. (http://www.sbfisica.org.br/bjp) 11 pages, 6 figures, 1 table, LaTex 2

Equity and Achievement in the Chilean School Choice Experience

The aim of this paper is to analyze, using a hierarchical linear model, the degree to which a system of choice, as the one implemented in Chile since the beginning of the 80’s, can promote student achievement and equity in the social distribution of achievement. Using data from a standardized achievement test including 226,860 4tth degree students and 4,949 schools, we investigate the association between students’ SES and achievement, within and between schools. We also investigate up to what extent different categories of schools enjoy advantages in educating low-income students. These are important issues because unlike the limited vouchers programs in the US, Chile has had a nationwide school choice program for more than 20 yearseducation vouchers, achievement, equity,

Fixed point theorems for generalized contractions on partial metric spaces

We obtain two fixed point theorems for complete partial metric space that, by one hand, clarify and improve some results that have been recently published in Topology and its Applications, and, on the other hand, generalize in several directions the celebrated Boyd and Wong fixed point theorem and Matkowski fixed point theorem, respectively.The author thanks the support of the Spanish Ministry of Science and Innovation, under grant MTM2009-12872-C02-01.Romaguera Bonilla, S. (2012). Fixed point theorems for generalized contractions on partial metric spaces. Topology and its Applications. 159:194-199. https://doi.org/10.1016/j.topol.2011.08.026S19419915

Quasi-pseudo-metrization of topological preordered spaces

We establish that every second countable completely regularly preordered space (E,T,\leq) is quasi-pseudo-metrizable, in the sense that there is a quasi-pseudo-metric p on E for which the pseudo-metric p\veep^-1 induces T and the graph of \leq is exactly the set {(x,y): p(x,y)=0}. In the ordered case it is proved that these spaces can be characterized as being order homeomorphic to subspaces of the ordered Hilbert cube. The connection with quasi-pseudo-metrization results obtained in bitopology is clarified. In particular, strictly quasi-pseudometrizable ordered spaces are characterized as being order homeomorphic to order subspaces of the ordered Hilbert cube.Comment: Latex2e, 20 pages. v2: minor changes in the proof of theorem 2.

T_0*-compactification in the hyperspace

A *-compactification of a T0 quasi-uniform space (X,U) is a compact T0 quasi-uniform space (Y,V) that has a T(V∨V−1)-dense subspace quasi-isomorphic to (X,U). In this paper we study when the hyperspace with the Hausdorff–Bourbaki quasi-uniformity is *-compactifiable and describe some of its *-compactifications.Kunzi, HA.; Romaguera Bonilla, S.; Sanchez Granero, MA. (2012). T_0*-compactification in the hyperspace. Topology and its Applications. 159:1815-1819. doi:10.1016/j.topol.2011.06.064S1815181915

Stimmt das Volumen der Pipette?

Nahezu jedes Labor nutzt Kolbenhubpipetten mit Luftpolster, im allgemeinen Sprachgebrauch oft als Mikroliterpipetten bezeichnet. Diese sind im Rahmen der Prüfmittelüberwachung regelmäßig zu kalibrieren. Da Faktoren wie Luftfeuchtigkeit und Temperatur die Ergebnisse stark beeinflussen, sind die Prüfbedingungen exakt einzuhalten. Worauf kommt es wirklich an